1. Field of the Invention
The present invention relates to an optical fluidic system.
2. Discussion of the Background Art
One may wish to subject fluids to light for several reasons. Two of which are the following: performance of photochemical reactions and the performance of optical detection.
Photochemical reactions may include photo polymerization or photochemical cleavage of molecules in smaller units. Both are well described in the literature and the applications are usually performed in devices having pilot plant size or technical size.
Optical detection of fluidic samples succeeding to chemical separation or preparation is a most preferred technique due to characteristics of being applicable without interfering in the chemical system being in the focus. In order to perform such optical detection generally a measuring chamber for the reception of the fluid, a light emitting and a light receiving device are needed. Performing online detection means designing a measuring chamber as a flow through cell. One may perform transmission or absorption measurements which are corresponding as indicated by optical laws such as Beer's law, which is known to those skilled in the art. Whichever technique is chosen, it presumes guiding light through the sample, accordingly a light path between a light emitting and a light receiving means is provided. Simplified, light emitting and light receiving means comprise a light source, detector and the corresponding waveguides. Applying Beer's law furthermore means knowing precisely the geometrical dimensions of the measuring device as far as they are needed to determine optical coefficients such as e.g. extinction.
Online detection is advantageously performed in a detection system which prevents turbulences followed by mixing of the sample due to dead volumes or changes of the cross sectional area of the fluid conducting device. The reliability on measuring results is based on providing a disturbance free fluid flow, allowing to measure variations of the fluid composition with the time. Performing optical detection techniques with devices designed for micro fluidic applications is still challenging since the advantage of needing only micro volumes of sample is accompanied by an increased request on the design, which should be adapted to the specific pressure and flow through characteristics, only to name some of the relevant parameters.
A device for microfluidic optical detections is described in U.S. Pat. No. 6,281,975, to Munk. He describes a capillary flow cell with protruding bulb ends providing a high light throughput entrance window for the cell, aiming for an improved sample illumination.
EP 0,089,157 to Le Febre discloses an optical detector cell for determining the presence of a solute in a sample fluid, for the particular application in miniature chromatographic and micro spectroscopic applications. An optical flow path which is parallel to the fluid flow path is provided, allowing maximizing of the sample corresponding to a fixed sample volume, whereby the ability results to measure low threshold concentrations in solutes.
U.S. Pat. No. 4,477,186 to Carlson refers to a photometric cuvette for optical analysis of through flowing media, designed for the measurement of minimum sample amounts.